The present application relates to polymer actuators, which function as actuators by bending or deforming their ionically conductive polymer layers.
Demands have been made on compact, lightweight, and flexible actuators in fields including medical devices, industrial robots, and micromachines. Actuators operating according to various principles have been proposed to meet these demands. Such actuators operate by the actions of, for example, electrostatic attraction, piezoelectricity, ultrasound, shape-memory effects of shape-memory alloys, and expansion/contraction of polymers.
Polymer actuators using ionically conductive polymers are categorized as actuators operating by the action of expansion/contraction of polymers. The polymer actuators have been expected as novel actuators, because they are lightweight and can deliver large force. These polymer actuators each include an ionically conductive polymer layer (ion-exchange resin membrane) and a pair of metal electrodes sandwiching the ionically conductive polymer layer. The pair of metal electrodes are insulated from each other. The ionically conductive polymer layer bends or deforms by incorporating water into the ionically conductive polymer layer and applying a voltage between the metal electrodes. The properties of actuators of this mechanism , such as deformation magnitude and delivered force, vary depending typically on materials and structure of the electrodes.
As possible solutions to these problems, Japanese Patent No. 2961125 and Japanese Unexamined Patent Application Publication (JP-A) No. 11-206162 propose actuators that may have an increased deformation magnitude and may deliver greater force. These actuators have electrodes having large specific surface areas at the interfaces with an ionically conductive polymer. The electrodes are formed by a plating technique, in which an ionically conductive polymer layer is allowed to adsorb a complex typically of gold or platinum, and the adsorbed complex is reduced using a reducing agent to deposit gold or platinum as the electrodes.
However, when films or membranes as electrodes are prepared from a noble metal by the plating technique, the film deposition rate is low, the resulting film shows a large variation, a special chemical should be used, and dedicated facilities should be used. Accordingly, it is difficult to produce actuators having stable performance at low cost in commercial production according to this technique.